The Collaborative International Dictionary of English v.0.48:

Supplement \Sup"ple*ment\, v. t. [imp. & p. p. Supplemented;
   p. pr. & vb. n. Supplementing.]
   To fill up or supply by addition; to add something to.
   [1913 Webster]

         Causes of one kind must be supplemented by bringing to
         bear upon them a causation of another kind. --I.
                                                  Taylor.
   [1913 Webster] Supplemental